1. Field of the Invention
The present invention relates to an antenna system and a method for reporting Reference Signal Receiving Power (RSRP) of the same, and more particularly to a distributed antenna system (DAS) and a method for reporting RSRP of the same.
2. Description of the Prior Art
In downlink Multiple Input Multiple Output (MIMO), a typical case of a DAS is deploying distributed antennas for indoor and outdoor use. The DAS is different from a conventional centralized wire system in that, path loss from distributed antenna ports at different geographical positions to a user equipment (UE) is different, thereby often causing the problem of unbalanced power. In order to solve the problem of unbalanced power, some technical solutions of adjustment and improvement may be performed at an evolved Node Base (eNB) side, in which the technical solutions include power compensation, transport point selection, and the like. These technical solutions require channel information of path loss of different transport points; however, in the current DAS, the eNB cannot obtain the information.
An application scenario of distributed antennas shown in FIG. 1 is taken as an example. In the scenario, an eNB 500 is disposed in a cell 50. In the figure, only a part of a macro base station (BS) node is shown. The eNB 500 allocates four distributed antennas 501, 502, 503, and 504 for serving a UE 505. The distributed antenna 501 is disposed on the macro BS node 500. Ports of the distributed antennas 501, 502, 503, and 504 are set to RRH0, RRH1, RRH2, and RRH3 respectively. Although reference signals, for example, channel state information-reference signals (CSI-RSs) CSI-RS0, CSI-RS1, CSI-RS2, and CSI-RS3, of the distributed antennas 501, 502, 503, and 504 are transparent to the UE 505, the UE 505 can report only one RSRP value to the eNB 500. Generally, the RSRP value is obtained by the UE 505 averaging measured RSRP0 and RSRP1 of the ports RRH0 and RRH1 of the distributed antennas. Due to lack of channel information of path loss of the distributed antennas 501, 502, 503, and 504, the eNB 500 cannot solve the problem of unbalanced power.
In fact, since the eNB cannot know the channel information of path loss of each distributed antenna, other problems, such as being inconvenient for transport point selection, being incapable of flexibly allocating resources, and reducing the system throughput, may be caused.
Therefore, the existing DAS and the method for reporting the RSRP need to be improved, to fundamentally solve the problem of unbalanced power.